Mehmet Scholl, who won eight Bundesliga titles with Bayern Munich and was their reserve team coach under Van Gaal, believes the Dutchman is a "genius coach" who will guarantee success for United. But he is unsure how long this will last.

Van Gaal is expected to be appointed by the middle of next week – he wants a deal in place by 7 May when he joins his Dutch-based players to begin their World Cup preparation. And Scholl told the Guardian: "He's very strict and severe. So the players just have the chance to follow him or they are out and he takes the next players. He's very good with young players. I think everywhere he was he had some problems with big players and the staff."

Van Gaal, who is the Holland coach until after the summer's World Cup, has previously managed Ajax, Barcelona, AZ Alkmaar and Bayern during his club career. Though he has won championships with all of these teams, the 62-year-old's longest tenure was his six years at Ajax before spending three at Barca, four with AZ and two at Bayern.

Asked how Van Gaal has achieved this success if he can fall out with senior players and staff, Scholl said: "There are 26, 27 players and he is looking for the 14 to follow him – 14, 15, 16 to follow. His thing is not the motivation [man-management]. He's good in motivation but this is not his main character thing.

"His thing is really working on the pitch – that's brilliant. And that's how the players learn. You know by yourself that if you learn from somebody you are curious, you want to learn more.

"Some of the players, I can tell you, like Rooney, I don't think he has to learn anything more. So that will be difficult for him if the coach says: 'You have to do it in a completely different way. Whatever you did until now, change it.'"

While Rooney is United's highest-paid player, Van Gaal enjoys a close relationship with Robin van Persie, the club's next best-rewarded footballer, naming his countryman as Holland captain, and the pair were regularly seen together at matches during Van Persie's recent recuperation from a knee injury. "I think the education is the thing," said the former midfielder Scholl. "The thing Van Gaal teaches is the same thing Van Persie learned from the very beginning. So there, I think, there will be no big problem. Of course he is a big player but he is a Dutch player. That's the thing and the difference to Rooney."

Asked about Van Gaal often staying for only truncated periods with clubs, Scholl said: "Yeah, I think he's for the moment exactly the right coach for United and United will be successful again with him. That's without doubt. That will come. The thing is he is very – he wants a lot of things from the players and, for the players, it is not easy to satisfy him all the time and so after several months, one or two years, it gets less what the players learn.

"We're not computers. Sometimes the brain is full. And he still wants [you] to learn, to learn, to learn, high level, every day. Is it annoying? No. It's exhausting. They lose power. That's what happened at Bayern Munich.

"And that's why he often picks young players because they learn and learn and learn. I don't know if he is working still the same. I just can tell you what happened in Bayern Munich."

Van Gaal's CV shows four Eredivisie titles, two in La Liga, one Bundesliga, the Champions League and Uefa Cup plus various other trophies for the clubs he has led. "He's a brilliant football coach. The way he likes his team to play is absolutely brilliant," Scholl, 43, said. "His main thing is to keep the ball, to be proactive not passive. He is a genius, he's one of the best I've ever seen on the pitch.

" For the big stars it is not easy to work with him but for the young players he is brilliant. He is brilliant on the pitch and wants them to learn all the time, wants them to learn. Even the old players."

Manchester City's chief executive Ferran Soriano, who worked at Barcelona together with Van Gaal, also believes that some of the players will find the Dutchman difficult. "If you treat your people badly, they remember," he said at a conference earlier this year. "One day you make an error and they kill you. I've seen this in many clubs. Louis van Gaal has been a very good coach in many clubs but his style is very difficult. The same thing happened to him in Barcelona as in Bayern Munich."

"He is very tough, people don't like him, but he wins. And one day you don't win — and when you don't win, everybody that is angry with you will come back to you and try to kill you. In the movies this works, in real life it doesn't."